With the high cost of mattresses, more and more people were attempting to find a good foam mattress topper to add comfort to their existing mattress and thereby obviate the need for a new mattress. The thickness of the topper is usually between one and four inches. Over four inches would be too high to fit an existing bed, and less than one inch would not be provide enough material to provide the needed comfort needed. Toppers are typically fabricated from several variations of latex, polyurethane, and memory foams of differing indentation load deflection (ILD) and weight.
Patent Application U.S. 2003/0097715 illustrates a selectively contoured single unibody foam piece for use as a layer in a cushioned load bearing structure has a first zone with a first surface topography having distinct support properties from a second zone with a second surface topography. The zones of differing topography are formed in the surface of a single, unibody piece of foam by applicable foam cutting techniques. Patterned removal of foam material from a single piece creates zones with different density, ILD or other load bearing properties with different support and feel characteristics. A single unibody component in a responsive flexible support structure has distinct zones with distinct support characteristics, the zones corresponding in location with the anticipated loads and loading patterns of a flexible support device in use.
U.S. Pat. Re. 32,734 discloses a cushion or mattress assembly having first and second resilient support surfaces of varying firmness each secured to a center piece stiffener board. The stiffener board is formed from a plurality of hinged sections allowing flexure of the stiffener board in one direction only, as well as allowing the entire assembly to be folded or rolled up for storage.